Bullshit. Here's why:
Q: .3 ratio
W: .4 ratio
E: .4 ratio
R: .8 ratio + .45/.6/.75 ratio over three hits
The only decent AP scaling Leo has is on her ult, which isn't available until level 6 and is on a long CD. This is like building Shyv AP because her ult has a .7 ratio on it. No one does that, because they don't want to waste gold buying a stat that only really contributes once every minute or so. Leo's other AP ratios are garbage. She has excellent base damages, which means her abilities scale better with CDR (so you can use the base damages more and more often) rather than AD or AP.
However, Leo does have one of the highest base ADs in the game at level 1 (60, compared to the highest of Mao at 63.5 and lowest of Ori at 40.3). Her AD growth is solidly middle of the pack, so her AD ends up being fairly good at level 18. That means she can abuse things that use base AD like Trinity and Steraks much better than other champs. The AD from those items is actually more useful than AP, since her auto attacks have a 1.0 AD ratio, her Q is a reset and also has a 1.0 ratio since it's an auto attack, and both her autos and Q are on a significantly lower CD than the rest of her kit.
So she won't lose much ability damage at all building AD over AP, but she will gain better auto attacks to CS and trade with. Since Leo is generally built with tank stats somewhere in her build no matter what you do, she can also take advantage of Titanic's HP scaling pretty well, giving her even more damage on her autos and a very quick waveclear when combined with W.
Top lane Leo is the kind of champion that wants long, extended trades where she just wears you down with stuns and autos and mixed damage, while transitioning into a CC tank late game when her damages fall off.
